Alkali recovery using PVA/SiO2 cation exchange membranes with different -COOH contents

► Multi-alkoxy copolymers with different -COOH groups content were developed. ► Membranes possess high thermal stabilities and acceptable swelling resistance. ► Effect of -COOH groups content were investigated. ► Membranes can be potentially applied in recovery of NaOH from the spent liquor.